The auto storage class specifier

The auto storage class specifier lets you explicitly declare a variable with automatic storage. The auto storage class is the default for variables declared inside a block. A variable x that has automatic storage is deleted when the block in which x was declared exits.

You can only apply the auto storage class specifier to names of variables declared in a block or to names of function parameters. However, these names by default have automatic storage. Therefore the storage class specifier auto is usually redundant in a data declaration.

Note: In C++11, the keyword auto is no longer used as a storage class specifier. Instead, it is used as a type specifier. The compiler deduces the type of an auto variable from the type of its initializer expression. For more information, see The auto type specifier (C++11).